Vapor accumulation in ethanol to jet fuel process

Abstract

An ethanol dehydration process is disclosed. The method includes adding an amount of steam to the feed to the dehydration reactor to provide a feed stream. The steam stream is mixed with the feed to the dehydration reactor such that the ratio of steam to ethanol is between about 0.5 weight / weight and about 5.0 weight / weight. The feed stream is passed to a dehydration reactor to produce a dehydrated stream. Steam may be input from outside the dehydration process, such as from oligomerization or dimerization reactions. Steam may be generated from the dehydrated stream.

Description

[0001] This application claims priority to U.S. Application 18 / 457,222 filed August 28, 2023, which claims priority to Indian Provisional Patent Application 202211049526 filed August 30, 2022. TECHNICAL FIELD

[0002] The present invention relates to the conversion of olefins to distillates. More specifically, the present invention relates to the production of steam during the oligomerization of olefins to distillate fuels by an ethanol to jet fuel process. BACKGROUND

[0003] Oil and gas refineries worldwide are exploring methods and routes to reduce carbon footprint and are moving towards sustainable processes. The process of ethanol to jet fuel is one of the routes that has the promise of minimizing or eliminating the carbon footprint of the consumer. The end products of the process are jet and diesel fuels produced from bioethanol. Jet fuel is a sustainable aviation fuel and is intended to replace jet fuel produced from conventional sources such as crude oil.

[0004] There are often three main steps in the process of converting ethanol to jet fuel. The first step is to dehydrate ethanol to produce ethylene. The ethylene is then converted to long chain olefins which are then hydrogenated to produce paraffins. The dehydration step of ethanol can require steam injection to get the desired catalyst life as well as to maintain the operation below the maximum heat absorption in an adiabatic system. The dehydration of ethanol can require a large amount of steam. The production of steam from product water can be energy intensive for the overall process. Efficient ways are needed to address the steam requirement of the ethanol dehydration step. SUMMARY

[0005] The present disclosure is directed primarily to the use of steam that can be produced during the oligomerization process to convert ethylene or other light olefins to longer chain olefins.

[0006] A method for operating a dehydration reactor is provided, the method comprising adding an amount of steam to a feed to the dehydration reactor, wherein the steam is taken from an oligomerization section of a hydrocarbon conversion plant.

[0007] In one embodiment, a method for dehydration of ethanol is provided, the method comprising adding an amount of steam to an ethanol feed stream, wherein the ratio of steam to ethanol is between 0.3 weight / weight to 5.0 weight / weight, and reacting the ethanol feed stream in the presence of a catalyst under reaction conditions to produce an ethylene effluent stream.

[0008] In another embodiment, a method for operating a dehydration reactor is provided, the method comprising adding a steam stream to a feed to the dehydration reactor to produce a charged stream; dehydrating the charged stream to produce a dehydrated stream; cooling the dehydrated stream to separate a water stream; and producing the steam stream from the separated water stream. A further embodiment provides a method for operating a dehydration reactor, the method comprising adding a steam stream to a feed to the dehydration reactor to produce a charged stream; dehydrating the charged stream to produce a dehydrated stream; cooling the dehydrated stream to separate a water stream; and heating the separated water stream with an oligomerization stage's olefin charged stream to produce the steam stream. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 is a schematic process flow diagram including an ethanol dehydration reactor

[0010] Figure 2 is shown a schematic diagram including a series of steam generators that provide steam to Figure 1 both the oligomerization reactor and the ethanol dehydration reactor of

[0011] Definitions

[0012] The term "in communication" means operable to allow the flow of fluids between the components listed, which can be characterized as "fluid communication."

[0013] The term "downstream communication" means that at least a portion of the material flowing to the subject in the downstream communication can operably flow from the object in communication therewith.

[0014] The term "upstream communication" means that at least a portion of the material flowing from the subject in the upstream communication can operably flow to the object in communication therewith.

[0015] The term "direct communication" means that the flow from an upstream component enters a downstream component without passing through a fractionation or conversion unit, without a change in composition due to physical fractionation or chemical conversion.

[0016] The term "indirect communication" means that the flow from an upstream component enters a downstream component after passing through a fractionation or conversion unit, with a change in composition due to physical fractionation or chemical conversion.

[0017] The term "bypass" means that the object is disconnected from downstream communication with the bypass subject at least in the range of the bypass.

[0018] The term "column" means one or more distillation columns for separating one or more components having different volatilities. Unless otherwise indicated, each column includes a condenser on the overhead of the column for condensing and refluxing a portion of the overhead stream back to the top of the column, and a reboiler at the bottom of the column for vaporizing and sending a portion of the bottoms stream back to the bottom of the column. The feed to the column can be preheated. The overhead pressure is the pressure of the overhead vapor at the vapor outlet of the column. The bottoms temperature is the liquid bottoms outlet temperature. Overhead and bottoms lines refer to the net lines downstream from the column that do not arbitrarily reflux or reboil to the column. A stripper column can omit the reboiler at the bottom of the column and instead provide for heating requirements and separation power to a liquefied inert medium such as steam. A stripper column is typically fed from the top tray and takes the main product from the bottom.

[0019] As used herein, the term "rich component stream" means that the rich stream coming out of a vessel has a greater concentration of a component than the feed to the vessel.

[0020] As used herein, the term "lean component stream" means that the lean stream coming out of a vessel has a lesser concentration of a component than the feed to the vessel.

[0021] As used herein, the term "separator" means a vessel having one inlet and at least one overhead vapor outlet and one bottoms liquid outlet, and can also have an aqueous stream outlet from a boot. A flash tank is one type of separator that can communicate downstream from a separator that can operate at higher pressures.

[0022] As used herein, the terms "majority" or "major" mean greater than 50%, suitably greater than 75%, and preferably greater than 90%.

[0023] As used herein, the term "true boiling point" (TBP) means the test method for determining the boiling point of a substance in accordance with ASTM D-2892 for the production of liquefied petroleum gases, distillate fractions, and residuum of standardized quality on which analytical data can be obtained, and determination of the yield of the above fractions by both mass and volume, using fifteen theoretical plates in a column with a reflux ratio of 5: 1 to obtain a plot of distillation temperature versus mass %.

[0024] As used herein, the terms "T5", "T90", or "T95" mean the temperature at which 5 mass percent, 90 mass percent, or 95 mass percent, as the case can be, of a sample boils using ASTM D-86 or TBP.

[0025] As used herein, the term "initial boiling point" (IBP) means the temperature at which a sample begins to boil using ASTM D-7169, ASTM D-86, or TBP, as the case can be.

[0026] As used herein, the term "end point" (EP) means the temperature at which the sample is all boiled off using ASTM D-7169, ASTM D-86, or TBP, as appropriate.

[0027] As used herein, the term "diesel" means hydrocarbons boiling in the range of IBP between about 125°C (257°F) and about 175°C (347°F), or T5 between about 150°C (302°F) and about 200°C (392°F), and "diesel cut points," including T95 between about 343°C (650°F) and about 399°C (750°F) using TBP distillation method, or T90 between 280°C (536°F) and about 340°C (644°F) using ASTM D-86. The term "green diesel" means a diesel comprising hydrocarbons not derived from fossil fuels.

[0028] As used herein, the term "jet fuel" means hydrocarbons boiling in the range of T10 boiling in the range of between about 190°C (374°F) and about 215°C (419°F) and having an end point of between about 290°C (554°F) and about 310°C (590°F). The term "green jet fuel" means a jet fuel comprising hydrocarbons not derived from fossil fuels.

[0029] As used herein, the term "C x " is understood to mean a molecule having a number of carbon atoms represented by the subscript "x." Similarly, the term "C x -" means a molecule containing less than or equal to x, and preferably x and fewer, carbon atoms. The term "C x +" means a molecule having greater than or equal to x, and preferably x and more, carbon atoms.

[0030] As used herein, the term "carbon number" refers to the number of carbon atoms per hydrocarbon molecule and typically a paraffin molecule. DETAILED DESCRIPTION

[0031] The disclosed process involves dimerizing and oligomerizing an olefin stream comprising ethylene, followed by further oligomerization of the ethylene oligomers. The process uses a zeolite catalyst for ethylene oligomerization in a first stage, and a metal catalyst for olefin oligomerization in a second stage.

[0032] In Figure 1 , a process 10 for processing an oxygenate feedstock is shown according to an exemplary embodiment. The oxygenate feedstock can comprise an alcohol, and preferably comprises ethanol. The feedstock can comprise primarily ethanol and can be aqueous. Preferably, the oxygenate feedstock is a biorenewable feedstock.

[0033] Feed line 12 delivers an oxygenate stream of oxygenate feedstock to a feed pretreatment section 14. The feed pretreatment section 14 includes a vessel 16 containing a bed of cation exchange resin adsorbent for removing metal contaminants, such as sodium, zinc, phosphates, copper, and calcium, as well as any basic compounds, from the oxygenate stream in feed line 12. The feed pretreatment section 14 can include an additional vessel 18 with the same adsorbent bed for further removal of metals from the oxygenate stream. The vessels 16, 18 can be in series or in a lead-lag type arrangement to allow for regeneration or replacement of spent adsorbent. Line 17 delivers the partially pretreated oxygenate stream from the outlet of vessel 16 to the inlet of vessel 18. The pretreated oxygenate stream exits the feed pretreatment section 14 in line 20 from the outlet of additional vessel 18 and is fed to a purification column 22. The feed pretreatment section 14 can be operated at a temperature of about 32°C to about 104°C or about 32°C to about 80°C and a pressure of about atmospheric pressure to about 670 kPa (g).

[0034] In the purification column 22, the pretreated oxygenate stream is fractionated to separate ethanol from heavier oxygenates, also known as fusel oils, such as cyclohexanol, cyclopentanol, and heavier alcohols and acids. The purification column 22 is operated to minimize ethanol to no more than 1% of the feed in the column bottoms stream in line 26. The heavy oxygenate stream in bottoms line 26 is withdrawn from the bottom of the purification column 22 for heavy oxygenate treatment. The purification column 22 can be reboiled by heat exchange with a suitable hot stream, such as steam, to provide the heat required for distillation. The purification column 22 provides an overhead gaseous stream of purified ethanol in overhead line 24, which can be cooled in air cooler 25 and fed to a feed surge tank 26 along with a circulating ethanol stream in line 27. The purification column 22 can be operated with a bottom temperature of between about 82°C and about 121°C and a top pressure of about 35 kPa (g) to about 140 kPa (g).

[0035] Ethanol feed comes from either a wet or dry milling process. These ethanol feeds can contain a variety of contaminants, such as higher alcohols, metals, acetaldehyde, ethyl acetate, etc. In addition, dry mill feed can also contain fusel oils (heavier alcohols and acids). The ethanol feed can be treated by using a resin treater to remove metal contaminants. Heavy hydrocarbons from the fresh feed can be separated out in a feed purification column.

[0036] Fresh ethanol feed can be combined with unconverted ethanol and split into two equal streams into parallel combined feed exchangers. Split reactor configurations are contemplated as maintaining the desired steam to ethanol ratio at the reactor inlet to maintain reactor endothermicity as well as to ensure catalyst stability. To minimize the combined feed rate to the reactor, it becomes necessary to reduce steam uptake. The ethanol dehydration reaction results in the production of water as a byproduct. The ethanol dehydration process requires steam injection in the process to achieve the desired catalyst life as well as to maintain operation below the maximum endotherm in an adiabatic system. It has been established that the optimal steam to ethanol ratio should be between about 0.5 weight / weight to about 5.0 weight / weight, or preferably between about 1.0 weight / weight to 2.0 weight / weight. In addition to this, some of the columns in the unit, including the feed purification column and the wastewater stripping column, can also be reboiled with steam. As the ethanol dehydration reactor operates in the gas phase, steam generation from product water can be energy intensive (product water is condensed and vaporized). To overcome this problem, it has been concluded that it is preferable to import steam from outside the dehydration boundary at about 100 psig. The exothermic oligomerization and hydrogenation reactions can be a good source of steam generation and there is a good opportunity to meet the steam demand. Steam can be taken from either or both of the oligomerization and hydrogenation reaction sections.

[0037] The oligomerization step of the ethanol to jet fuel process uses a high temperature reactor at a front end location. Steam generation can be used to achieve inter-bed temperature control. The steam level can be set at a pressure of about 100 psig to cool the hot effluent down to a minimum of about 370°F (187°C). A steam generator using hot diesel from the jet fuel fractionator bottoms can be used to ensure that sufficient steam is generated for ethanol dehydration.

[0038] For a 300 MMGPY ethanol unit, the combined steam flow is estimated to be about 140 k lb / hr, which can meet the ethanol dehydration steam injection requirement.

[0039] The ethanol in the feed buffer tank 26 can be blanketed with nitrogen. A charge pump 29 pumps the ethanol charge stream in line 28 into two charge streams. The first charge stream in line 30 is heat exchanged with the first dehydration exchange stream in line 32, mixed with a steam stream in line 33, and fed to a first charge heater 34. The first charge heater 34 can be a fired heater and can heat the first charge stream to about 400°C to about 550°C. The resulting first heated charge stream in line 36 is charged to a first dehydration reactor 40. In the first dehydration reactor 40, the ethanol feed is converted to ethylene and water over a dehydration catalyst at a pressure of about 379 kPa (a) to about 690 kPa (a), or about 455 kPa (g) to about 630 kPa (g). A first dehydration stream is discharged from the first dehydration reactor 40 via line 42.

[0040] The second charge stream in line 44 is heat exchanged with the second dehydrated exchange stream in line 46, mixed with the first dehydrated stream in line 42, and fed to a second charge heater 48. The second charge heater 48 can be a fired heater and can heat the second charge stream to about 400°C to about 550°C. The resulting second heated charge stream in line 50 is charged to a second dehydrated reactor 52. In the second dehydrated reactor 52, the ethanol feed is converted to ethylene and water over a dehydration catalyst at a pressure of about 420 kPa(g) to about 700 kPa(g). The second dehydrated stream is withdrawn from the second dehydrated reactor 52 via line 54.

[0041] The second dehydrated stream in line 54 is fed to an intermediate heater 56. The intermediate heater 56 can be a fired heater and can heat the second dehydrated stream to about 400°C to about 550°C. The resulting third heated charge stream in line 58 is charged to a third dehydrated reactor 60. In the third dehydrated reactor 60, the remaining ethanol feed is converted to ethylene and water over a dehydration catalyst at a pressure of about 420 kPa(g) to about 700 kPa(g). The third dehydrated stream is withdrawn from the third dehydrated reactor 60 via line 62.

[0042] The dehydration catalyst can be an alumina-based catalyst.

[0043] The third dehydrated stream is split between the first dehydrated exchange stream in line 32 and the second dehydrated exchange stream in line 46. The first dehydrated exchange stream in line 32 is heat exchanged with the first charge stream in line 30, and the second dehydrated exchange stream in line 46 is heat exchanged with the second charge stream in line 44, and the cooled dehydrated stream is recombined in line 64.

[0044] The cooled dehydrated stream in line 64 is fed to a quench column 68 where the cooled dehydrated stream is quenched by direct contact with water from a first cooling water stream in line 70 and a second cooling water stream in line 72. The quenched ethylene stream flows out of the top of the quench column in line 74 and a bottoms water stream flows out of the bottom in line 76. The bottoms water stream splits between a blowdown stream in line 78, which blowdown stream can be sent to a waste water stripper 80 through a control valve on it, and a quench recycle stream in line 82. A first portion of the quench recycle stream is air cooled in a product condenser 69 and recycled as the first lower cooling water stream in line 70 through a control valve on it, and a second portion of the quench recycle stream is heat exchanged in a trim condenser 71 and recycled to the quench column 68 as the second higher cooling water stream in line 72. The quench column 68 can be operated with a bottoms temperature of about 37°C (100°F) to about 104°C (220°F) and a top pressure of about 280 kPa (gauge) (40 psig) to about 490 kPa (gauge) (70 psig).

[0045] The quenched ethylene stream in line 74 is fed to a first stage suction drum 86. In the first stage suction drum, ethylene flows out of the top in line 88 to a first stage compressor 90, while residual water flows out of the bottom of the drum in line 92 through a control valve on it and can be sent to the waste water stripper 80 through line 78. The first stage compressor 90 compresses the ethylene stream to a first pressure of about 350 kPa (gauge) (50 psig) to about 1225 kPa (gauge) (175 psig), and the blowdown in line 91 is cooled in a first stage blowdown cooler 93 and a first stage trim cooler 94.

[0046] The cooled compressed ethylene stream from the first stage trim cooler 94 is fed to a first stage blowdown drum 96. Ethylene flows out of the first stage blowdown drum 96 in line 98 to a second stage compressor 100, while residual water flows out of the bottom of the drum in line 102 through a control valve on it and can be sent to the waste water stripper 80 through lines 92 and 78. The second stage compressor compresses the ethylene stream to a second pressure of about 455 kPa (g) to about 3220 kPa (g), and the blowdown in line 101 is cooled in a second stage blowdown cooler 103 and a second stage trim cooler 104.

[0047] The twice cooled compressed ethylene stream from the second stage trim cooler 104 is fed to a second stage blowdown drum 106. Ethylene flows out of the second stage blowdown drum 106 in line 108 and is sent to a water wash column 110, while a residual water stream flows out of the bottom of the drum in line 112 through a control valve on it and can be sent to the waste water stripper 80 through lines 102, 92, and 78.

[0048] In the water wash column 110, the secondarily cooled compressed ethylene stream is counter-currently washed with a cooled, treated water stream from the waste water stripper 80 in line 118 to absorb additional oxygenates, producing a washed ethylene stream that flows in overhead line 120 and a wash water stream in line 122. The washed ethylene stream in line 120 is sent to the caustic scrubber column 116. The wash water stream in line 122 is sent back to the water stripper 80 through a control valve on it. The wash water 110 can be operated with a bottom temperature of about 16°C to about 82°C and an overhead pressure of about 2800 kPa (g) to about 3500 kPa (g).

[0049] The caustic scrubber column 116 has a lower caustic scrubbing section 124 and an upper water wash section 132. In the lower caustic scrubbing section 124, the washed ethylene stream in line 120 is scrubbed with a caustic water stream from line 126 to absorb acidic gases such as carbon dioxide from the washed ethylene stream. Spent caustic is pumped from the bottom of the lower section in line 128 to the periphery and replenished with fresh caustic in line 130 to provide the caustic water stream 126. The scrubbed gaseous ethylene stream depleted of acidic gases rises from the caustic section 124 through a vapor inlet to the upper water wash section 132. In the water wash section 132, the scrubbed ethylene stream is contacted with a wash water stream from line 134. The washed, scrubbed gaseous ethylene stream flows out of the top of the water wash section 132 in line 136 and is fed to the product dryer section 140. A waste water stream is withdrawn from the bottom of the water wash section 132 from a liquid sump in line 142 and replenished with a fresh water stream from line 144 to provide the wash water stream in line 134 and pumped to the top of the water wash section 132 to contact the scrubbed gaseous ethylene stream. The caustic scrubber column can be operated with a bottom temperature of about 38°C to about 43°C and an overhead pressure of about 2800 kPa (g) to about 2975 kPa (g).

[0050] In the product dryer section 140, the scrubbed, gas-washed ethylene stream in line 136 is fed to a first dryer inlet knockout drum 146 to remove residual water and provide a dryer inlet stream in line 148 and a bottoms water stream in line 150, which can be fed to the waste water stripper 80 via line 122. The dryer inlet stream is fed via line 148 to a first product dryer 152. The first product dryer 152 includes a sorbent for adsorbing water from the ethylene in the dryer inlet stream in line 148 to provide a dry ethylene stream. The sorbent can be a molecular sieve material having a pore size of 2 A - 4 A. The first product dryer 152 can be operated in an upflow mode. The first product dryer 152 can be operated in a downflow mode. The product dryer section 140 can include a second product dryer 156 operated as the first product dryer 152. The two product dryers can be operated in series, but are preferably arranged in a lead-lag mode of operation to facilitate regeneration during continuous operation. Like the first product dryer 152, the second product dryer 156 includes a sorbent for adsorbing water from the ethylene. The dry ethylene stream flows out of the product dryer section 140 in line 158 as a dry ethylene stream. The product dryer section 140 can be operated at a temperature of about 32°C (90°F) to about 49°C (120°F) and a pressure of about 2758 kPa (gauge) (400 psig) to about 3102 kPa (gauge) (450 psig).

[0051] The dry ethylene stream in line 158 is fed to a dryer outlet knockout drum 160 to remove residual water and provide a dryer outlet stream in line 162 and a second separated water stream in line 164, which can be fed to the waste water stripper 80 via line 150 and line 122. The dryer outlet stream in line 162 can be fed to the heavy oxygenate removal column 170. In an aspect, the dryer outlet knockout drum 160 can be optionally used, and the dry ethylene stream in line 158 can be directly fed to the heavy oxygenate removal column 170.

[0052] The dryer outlet stream in line 162 can be fed to a heavy oxygenate removal column 170 to separate an overhead stream comprising primarily ethylene but possibly higher olefins from heavy ketones and diethyl ether. The olefins are produced in an overhead line 172 and fed to a third stage compressor 174 and a bottom heavy oxygenate stream is produced in a bottom line 176. The heavy oxygenate purge stream can be subjected to heavy oxygenate treatment in line 178 while a reboil portion is reboiled and fed back into column 170. The compressed ethylene stream in compressor discharge line 177 at a pressure of about 2800 kPa (gauge) (400 psig) to about 7000 kPa (gauge) (1000 psig) can be provided to the oligomerization section. The heavy oxygenate removal column 170 can be operated with a bottom temperature of about -28°C (-20°F) to about 122°C (250°F) and an overhead pressure of about 2413 kPa (g) (350 psig) to about 3103 kPa (g) (450 psig).

[0053] The water stream containing oxygenates and volatiles in lines 92, 102, 112, 122, 150, 164 can be fed to a waste water stripper column 80 where the volatiles and oxygenates are boiled off to provide an overhead volatiles stream in line 182 and a stripped water stream in line 184. A portion of the stripped water stream can be reboiled and fed back into the column to provide the necessary heat. The treated water stream in line 186 can be pumped to a water outlet in line 188 which includes the cooled treated water stream in line 118 for the water wash column 110. The waste water stripper column 80 can be operated with a bottom temperature of about 93°C (200°F) to about 121°C (250°F) and an overhead pressure of about 34 kPa (gauge) (5 psig) to about 138 kPa (gauge) (20 psig). In an aspect, a portion or all of the treated water stream in line 186 can be pumped to a steam generator to produce a steam stream in line 33.

[0054] The overhead volatiles stream in line 182 can be cooled in an air cooler 189 and fed to a waste gas knockout drum 190. The overhead stream from knockout drum 190 in line 192 can be sent to flare while an ethanol recycle stream can be pumped through line 24 to the feed buffer tank 26 in line 27. Alternatively, the overhead stream from knockout drum 190 in line 192 can be compressed and sent to fuel gas.

[0055] Figure 2 The oligomerization reactor column is shown along with a series of five steam generators from which a portion of the steam is sent to the ethanol dehydration column in line 33.

[0056] Turning to Figure 2The oligomerization section 210 supplies the feed olefin stream from line 212 to the oligomerization section 210. The feed olefin stream may contain a significant amount of ethylene and propylene. The feed olefin stream may primarily contain ethylene and / or propylene. In one aspect, the feed olefin stream may contain at least 95 mol% ethylene and / or propylene. The feed olefin stream in line 212 may be designed as a light olefin stream. Additional olefinic substances with a carbon number range of C4 to C6 are contemplated in the feed stream. The light olefin stream may be provided by dehydration of ethanol or from the MTO unit. The feed olefin stream may be at a temperature of about 60°C (140°F) to about 150°C (302°F), preferably about 80°C (176°F) to about 100°C (212°F) and a pressure of about 3.5 MPa (500 psig), preferably about 5.6 MPa (800 psig) to about 8.4 MPa (1200 psig).

[0057] The olefin feed stream may initially be contacted with a first-stage oligomerizing catalyst to oligomerize ethylene and propylene into oligomers, and then with a second oligomerizing catalyst to oligomerize the unconverted ethylene and propylene from the first-stage oligomerization. Alternatively, the olefin feed stream may first be contacted with a second-stage oligomerizing catalyst to oligomerize ethylene and propylene, and then with a first-stage oligomerizing catalyst to oligomerize the oligomerized ethylene and propylene.

[0058] Oligopolymerization reactions generate a significant amount of exothermic heat. For example, the dimerization of ethylene can generate 612 kcal / kg (1100 BTU / lb) of heat. Therefore, this significant exothermic heat must be managed. Consequently, the feed olefin stream in line 212 can be diverted into multiple olefin streams. Figure 2 In this embodiment, the feed olefin stream is split into two independent streams: a first feed olefin stream in a first feed olefin line 212a and a second feed olefin stream in a second feed olefin line 212b. More or fewer independent olefin streams can be used. Up to six feed olefin streams are readily conceivable. The feed olefin stream in line 212 can be split into multiple olefin streams of equal proportions. Alternatively, the feed olefin stream in line 212 can be split into unequal streams. For example, the feed olefin stream can be split into streams with decreasing flow rates, wherein the feed olefin stream to the preceding reactor has a greater flow rate than the feed olefin stream to the following reactor. In one embodiment, the feed olefin stream is split into two streams of equal flow rates, each stream containing 50% by volume of feed olefin stream. In another embodiment, the first feed olefin stream in the first feed olefin line 212a may account for about 70% to about 90% of the feed olefin stream in the line 212, and the second feed olefin stream in the second olefin line 212b may account for about 10% to about 30% of the feed olefin stream in the line 212.

[0059] To manage the heat release, the charge olefin stream can be diluted with a diluent stream to provide a diluted olefin stream to absorb the heat release. The diluent stream can comprise a paraffin stream in diluent line 214. The diluent stream in diluent line 214 can be added to the first charge olefin stream in first charge olefin line 212a before it is charged to the first stage oligomerization reactor 222. Preferably, the diluent stream is added to the first charge olefin stream in line 212a after the charge olefin stream in line 212 is split into multiple olefin streams to provide a first diluted olefin charge stream in line 216a, so the diluent stream passes through the entire first stage oligomerization reaction. Alternatively, the diluent stream can also be split into multiple streams, with each diluent stream being added to a corresponding charge olefin stream. The diluent stream can have a volumetric flow rate that is about 2 to about 8 times and preferably about 3 to about 6 times the volumetric flow rate of the charge olefin stream in charge olefin line 212.

[0060] The recycle olefin stream comprising C4to C8olefins in recycle line 226 can be mixed with the charge olefin stream and oligomerized in the first stage oligomerization reactor 222. In one embodiment, the recycle olefin stream in line 226 is split into multiple recycle olefin streams 226a, 226b, 226c, and 226d. The recycle olefin stream in first recycle olefin line 226a can be mixed with the first charge olefin stream in line 212a and charged to the first stage oligomerization reactor 222. In a further embodiment, the first recycle olefin stream in first recycle olefin line 226a is mixed with the first charge olefin stream in line 212a and the diluent stream in line 214 to provide a diluted first charge olefin stream in line 216a.

[0061] The first diluted olefin stream can comprise no more than 35 wt% olefins, suitably no more than 30 wt% olefins, and preferably no more than 20 wt% olefins. In one embodiment, the first diluted olefin stream comprises about 10 wt% to about 30 wt% C2to C8olefins. The first diluted olefin stream can comprise no more than 30 wt% ethylene, suitably no more than 25 wt% ethylene, and preferably no more than 20 wt% ethylene. In one embodiment, the first diluted charge olefin stream comprises about 10 wt% to about 20 wt% propylene. The first diluted olefin stream can comprise no more than 30 wt% propylene, suitably no more than 25 wt% propylene, and preferably no more than 20 wt% propylene. In one embodiment, the first diluted charge olefin stream comprises about 10 wt% to about 20 wt% propylene.

[0062] The first stage oligomerization reactor 222 can include a series of first stage oligomerization catalyst beds 222a, 222b, 222c, and 222d, each for loading with a dedicated olefin feed stream. The first stage oligomerization reactor 222 preferably contains four fixed first stage oligomerization catalyst beds 222a, 222b, 222c, and 222d. It is also contemplated that each first stage oligomerization catalyst bed 222a, 222b, 222c, and 222d can be in a dedicated first stage oligomerization reactor, or multiple first stage oligomerization catalyst beds can be in two or more independent first stage oligomerization vessels. It is readily contemplated that up to six first stage oligomerization catalyst beds. In Figure 2 In one embodiment, two first stage oligomerization reactor vessels 221a and 221b are used.

[0063] When the first stage oligomerization reactor 222 has been deactivated, a parallel first stage oligomerization reactor can be used during which the first stage oligomerization reactor 222 is regenerated in situ by burning the coke from the catalyst. In another embodiment, each first stage oligomerization reactor can include a front reactor, a lag reactor, and a backup reactor to facilitate regeneration. Figure 2 In one embodiment, only two reactor vessels 221a, 221b are shown.

[0064] The diluted first feed olefin stream in line 216a can be cooled in a first feed cooler 218a to provide a cooled diluted first feed olefin stream in line 220a and loaded into a first bed 222a of first stage oligomerization catalyst in a first first stage oligomerization reactor vessel 221a of the first stage oligomerization reactor 222. The cooled diluted first feed olefin stream in line 220a can be loaded at a temperature of about 180°C (356°F) to about 260°C (500°F) and a pressure of about 3.5 MPag (500 psig) to about 8.4 MPag (1200 psig). The feed cooler 218a can include a steam generator.

[0065] The diluted first feed olefin stream can be loaded into the first first stage catalyst bed 222a in line 220a, preferably in a downflow operation. However, an upflow operation can be suitable. As oligomerization of ethylene, propylene, and recycled olefins occurs in the first first stage oligomerization catalyst bed 222a, heat is generated due to the highly exothermic nature of the olefin oligomerization reaction. Despite cooling and dilution, oligomerization of the first feed olefin stream produces a first oligomerization effluent stream in a first oligomerization effluent line 224a at an elevated outlet temperature. The elevated outlet temperature is limited to between 150°C (302°F) and about 250°C (482°F).

[0066] The second charge olefin stream in line 212b can be mixed with the second recycle olefin stream in second recycle olefin line 226b and with the first oligomer effluent stream in first oligomer effluent line 224a removed from the first first-stage oligomer catalyst bed 222a in the first first-stage reactor 221a to provide a mixed second charge olefin stream in line 216b. The first oligomer effluent stream in line 224a includes the diluent stream from diluent line 214 that was added to the first olefin charge stream in line 212a. The second charge olefin stream can include no more than 35 wt% C2to C8olefins, suitably no more than 25 wt% C2to C8olefins, and preferably no more than 20 wt% ethylene. The second dilute olefin stream can include no more than 30 wt% ethylene, suitably no more than 25 wt% ethylene, and preferably no more than 20 wt% ethylene. The second dilute olefin stream can include no more than 30 wt% propylene, suitably no more than 25 wt% propylene, and preferably no more than 20 wt% propylene. The second charge olefin stream in line 216b can be cooled in a second charge cooler 218b located outside the first first-stage oligomer reactor 221a to provide a cooled second charge olefin stream in line 220b and charged into a second bed 222b of first-stage oligomer catalyst in the first first-stage oligomer reactor 221a. The second charge cooler 218b removes reaction heat from the first oligomer effluent stream in first oligomer effluent line 224a. The charge coolers 218a, 218b, 218c, 218d, and 218e can also be referred to as intermediate cooler steam generators, where the intermediate cooler steam generators remove reaction heat from the oligomer effluent stream before passing the oligomer effluent stream to a second oligomer reaction vessel. The intermediate cooler steam generator between the oligomer catalyst beds in the first oligomer reaction vessel 221a can remove reaction heat from the oligomer effluent stream of the top oligomer catalyst bed of the first oligomer reaction vessel 221a. The intermediate cooler steam generator between the oligomer catalyst beds in the second oligomer reaction vessel can remove reaction heat from the oligomer effluent stream of the top oligomer catalyst bed of the second oligomer reaction vessel 221b. In one embodiment, the oligomerization section includes a first-stage oligomer reactor 222 and a second-stage oligomer reactor 232 and an intermediate cooler steam generator 218e is provided to remove reaction heat from the oligomer effluent stream of the first-stage oligomer reactor 222 before passing the oligomer effluent stream to the second-stage oligomer reactor 232.

[0067] The second charge olefin stream in line 220b can be charged at a temperature of from about 180 °C (356 °F) to about 230 °C (446 °F) and a pressure of from about 3.5 MPag (500 psig) to about 8.4 MPag (1200 psig). The second charge olefin stream will comprise diluent and olefins from the first oligomer stream. The olefins from the first oligomer stream will oligomerize in the second catalyst bed 222b. Oligomerization of ethylene, propylene, recycled olefins, and oligomers in the second olefin stream in the second bed 222b of first stage oligomerization catalyst at elevated outlet temperatures produces a second oligomer effluent stream in a second oligomer effluent line 224b. The elevated outlet temperature can be limited to from 30 °C (54 °F) to about 50 °C (90 °F) higher than the inlet temperature of the catalyst bed 222b.

[0068] The second oligomer effluent stream in line 224b removed from the second bed 222b of first stage oligomerization catalyst in the first first stage reaction vessel 221a can be mixed with the third recycled olefin stream in the third recycled olefin line 226c to provide a first recycled olefin charge stream in line 216c. None of the charge olefin streams in line 212 are directly added to the first recycled olefin charge stream in line 216c. Alternatively, a portion of the charge olefin streams in line 212 can be charged with the second oligomer effluent stream and the first recycled olefin charge stream in line 216c. The second oligomer effluent stream in line 224b includes the diluent stream from the diluent line 214 that was added to the first charge olefin stream in line 212a. The first recycled olefin charge stream can comprise no more than 30 wt% ethylene, suitably no more than 25 wt% ethylene and preferably no more than 20 wt% ethylene. The first recycled olefin charge stream can comprise no more than 30 wt% propylene, suitably no more than 25 wt% propylene and preferably no more than 20 wt% propylene. The first recycled olefin charge stream can comprise no more than 30 wt% C2to C8olefins, suitably no more than 25 wt% C2to C8olefins and preferably no more than 20 wt% C2to C8olefins. The first recycled olefin charge stream in line 216c can be cooled in a third charge cooler 218c positioned outside the oligomerization reactor 222 to provide a cooled first recycled olefin charge stream in line 220c and charged to a third bed 222c of first stage oligomerization catalyst in the first stage oligomerization reactor 222. The third charge cooler 218c removes heat of reaction from the second oligomer effluent stream in line 224b. In one embodiment, the third bed 222c of first stage oligomerization catalyst is disposed in the second first stage reaction vessel 221b. The charge cooler 218c can comprise a steam generator.

[0069] The cooled first recycle olefin charge stream in line 220c can be charged at a temperature of from about 180°C (356°F) to about 230°C (446°F) and a pressure of from about 3.5 MPag (500 psig) to about 8.4 MPag (1200 psig). The first recycle olefin charge stream will include diluent as well as olefins from the second oligomerized olefin stream and the third recycle olefin stream. The olefins will be oligomerized in the third catalyst bed 222c. Oligomerization of ethylene and propylene in the third bed 222c of first stage oligomerization catalyst and oligomerization of oligomers in the first recycle olefin charge stream produces a third oligomer effluent stream in a third oligomer effluent line 224c at an elevated outlet temperature. In one embodiment, the third oligomer effluent stream is the penultimate oligomerized olefin stream and the third oligomer effluent line 224c is the penultimate oligomer effluent line 224c. The elevated outlet temperature is limited to from 30°C (54°F) to about 50°C (90°F) above the inlet temperature of the catalyst bed 222c.

[0070] The third oligomer effluent stream in line 224c removed from the second first stage oligomerization reactor vessel 221b of the first stage oligomerization reactor 222 can be mixed with the fourth recycle olefin stream in line 226d to provide a second recycle olefin charge stream in line 216d. The third oligomer effluent stream in line 224c includes a diluent stream from the diluent line 214 that was added to the first olefin stream in line 212a. None of the charge olefin streams in line 212 are added directly to the second recycle olefin charge stream in line 216d. In one embodiment, the third oligomer effluent stream in line 224c can also be mixed with and oligomerized with the olefin charge stream from the olefin charge line 222. The second recycle olefin charge stream can contain no more than 35 wt% C2to C8olefins, suitably no more than 30 wt% C2to C8olefins and preferably no more than 25 wt% C2to C8olefins. The second recycle olefin charge stream can contain no more than 30 wt% ethylene, suitably no more than 25 wt% ethylene and preferably no more than 20 wt% ethylene. The second recycle olefin charge stream can contain no more than 30 wt% propylene, suitably no more than 25 wt% propylene and preferably no more than 20 wt% propylene. The second recycle olefin charge stream in line 216d can be cooled in a fourth charge cooler 218d located outside of the second vessel 221b of the first stage oligomerization reactor 222 to provide a cooled second recycle olefin charge stream in line 220d and charged to a fourth bed 222d of first stage oligomerization catalyst in the second vessel of the first stage oligomerization reactor 222. The fourth charge cooler 218d removes heat of reaction from the third oligomer effluent stream in line 224c. The charge cooler 218d can include a steam generator.

[0071] The cooled second recycle olefin charge stream in line 20d can be charged at a temperature of about 180°C (356°F) to about 230°C (446°F) and a pressure of about 3.5 MPa (gauge) (500 psig) to about 8.4 MPa (gauge) (1200 psig). The cooled second recycle olefin charge stream in line 220d will include diluent and olefins from the third or penultimate oligomer effluent stream and C4-C8 olefins from the fourth recycle olefin stream. The olefins will be oligomerized over the fourth catalyst bed 222d. Oligomerization of ethylene and propylene in the second recycle olefin charge stream in the fourth bed 222d of the first stage oligomerization catalyst produces a fourth oligomer stream in a fourth oligomer effluent line 224d at an elevated outlet temperature. The elevated outlet temperature is limited to 30°C (54°F) to about 50°C (90°F) above the inlet temperature of the catalyst bed 222d.

[0072] The fourth oligomer effluent stream in line 224d exits the second reaction vessel 221b of the first stage oligomerization reactor 222. In one embodiment, the fourth oligomer effluent stream in line 224d is the last oligomer effluent stream and the fourth oligomer effluent line 224d is the last oligomer effluent line 224d.

[0073] The first stage oligomerization reaction occurs in the liquid phase or in a mixed liquid and gas phase based on the olefins at an LHSV of 0.5 hr1to 10 hr1. We have found that over the entire first stage oligomerization catalyst bed, typically 10 wt% to 50 wt% of the ethylene in the olefin stream is converted to higher olefins. The ethylene is initially catalytically dimerized to butenes. A major portion of the propylene and butenes in the olefin stream charged to the first stage oligomerization catalyst bed are oligomerized. In one embodiment, at least 99 mole% of the propylene and butenes in the olefin stream are oligomerized.

[0074] The first stage oligomerization catalyst can include a zeolite catalyst. The first stage oligomerization catalyst can be considered a solid acid catalyst. The zeolite can comprise between about 5 wt% and about 95 wt% of the catalyst, such as between about 5 wt% and about 85 wt%. Suitable zeolites include zeolites having a structure of one of the following classes: MFI, MEL, ITH, IMF, TUN, FER, BEA, FAU, BPH, MEI, MSE, MWW, UZM-8, MOR, OFF, MTW, TON, MTT, AFO, ATO, and AEL. The three letter codes indicating the classes of zeolites are as defined by the Structure Commission of the International Zeolite Association and are maintained at http: / / www.iza-structure.org / databases. UZM-8 is described in U.S. Patent No. 6,756,030. In preferred aspects, the first stage oligomerization catalyst can comprise a zeolite with a framework having a ten-ring pore structure. Examples of suitable zeolites having a ten-ring pore structure include TON, MTT, MFI, MEL, AFO, AEL, EUO, and FER. In further preferred aspects, the first stage oligomerization catalyst comprising a zeolite having a ten-ring pore structure can comprise a one-dimensional pore structure. One-dimensional pore structure indicates a zeolite containing non-crossing pores substantially parallel to one of the crystallographic axes. The pores preferably extend through the zeolite crystal. A suitable example of a zeolite having a ten-ring one-dimensional pore structure can include MTT. In additional aspects, the first stage oligomerization catalyst comprises a MTT zeolite.

[0075] The first stage oligomerization catalyst can be regenerated upon deactivation. Suitable regeneration conditions include subjecting the first stage oligomerization catalyst to hot air, for example, in situ, at about 400 °C to about 500 °C. To facilitate regeneration without shutdown, a swing bed arrangement can be employed with an alternative first stage oligomerization reactor. A regeneration gas stream can be brought into the first stage oligomerization reactor 222 in need of regeneration. The regeneration gas can include air with increased or decreased oxygen concentration. The activity and selectivity of the regenerated catalyst is comparable to fresh catalyst.

[0076] Zeolite catalysts are advantageous as first stage oligomerization catalysts. Zeolite catalysts have a relatively low sensitivity to oxygenate contamination. Thus, the olefin feed in line 212 requires a lesser degree of oxygenate removal if produced from an ethanol dehydration process.

[0077] The last first stage oligomer stream in the last first stage oligomer effluent line 224d has reduced concentrations of ethylene and propylene oligomers compared to the charged oligomer stream in line 212. The last first stage oligomer stream in the last first stage oligomer effluent line 224d is cooled by steam generation in steam generator 218e or by other heat exchange and is further cooled by heat exchange with the second stage oligomer stream in line 234 and possibly further cooled such as by an air cooler to provide a first stage oligomer stream and charged to the second stage oligomer reactor 232 in the second stage oligomer charge line 228. In an aspect, a steam generator 218e can be provided to remove heat of reaction from the last first stage oligomer effluent line 224d of the first stage oligomer reactor 222 prior to passing it to the second stage oligomer reactor 232. To achieve the most desirable olefin products, the second stage oligomer reactor 232 is operated at a temperature of about 80°C (176°F) to about 180°C (356°F). The second stage oligomer reactor 232 is operated at a pressure of about 2.1 MPa (300 psig) to about 7.6 MPa (1100 psig) and more preferably about 3.5 MPa (500 psig) to about 6.9 MPa (1000 psig).

[0078] The second stage oligomer reactor 232 can be in downstream communication with the first stage oligomer reactor 222. The second stage oligomer reactor 232 is preferably operated in a downflow operation. However, an upflow operation can be suitable. The second stage oligomer charge stream is contacted with a second stage oligomer catalyst to dimerize and trimerize unconverted ethylene from the first stage oligomer reactor 222, while higher olefins are also dimerized, trimerized, and tetramerized to provide olefins of a distillate boiling range. With respect to the second stage oligomer reactor 232, process conditions are selected to produce a higher percentage of jet range olefins which, when hydrogenated in a subsequent step to be described below, produce the desired jet range hydrocarbon products. A major portion of the unconverted ethylene from the first stage oligomer reactor 222 is dimerized, trimerized, and tetramerized. In one embodiment, at least 99 wt% of the ethylene in the second stage oligomer charge stream is converted primarily to butenes.

[0079] The second stage oligomer reactor 232 can include a first reaction vessel 231a including a first bed 232a of second stage oligomer catalyst and a second reaction vessel 231b including a second bed 232b of second stage oligomer catalyst. A first second stage oligomer stream is withdrawn from the first second stage reaction vessel 231a, cooled, and charged to the second second stage reaction vessel 231b. The second stage oligomer stream in line 234 exiting the second stage oligomer reactor 232 has an increased average carbon number over the charged first stage oligomer stream in line 228.

[0080] The second stage oligomerization catalyst is preferably an amorphous silica alumina base with metals from Group VIII and / or Group VIB of the Periodic Table using Chemical Abstracts Service (CAS) notation. In one aspect, the catalyst has a Group VIII metal promoted with a Group VIB metal. Typically, the silica and alumina are only in the base, so the silica / alumina ratio of the catalyst is the same as the base. The metals can be impregnated onto or ion exchanged with the silica alumina base. Co-milling is also contemplated. Catalysts for use in the present application can have a low temperature acidity ratio of at least about 0.15, suitably about 0.2, and preferably greater than about 0.25, as determined by the ammonia temperature programmed desorption method (ammonia TPD) as described below. In addition, a suitable catalyst will have a surface area of between about 50 m2 / g and about 400 m2 / g, as determined by nitrogen BET.

[0081] A preferred second stage oligomerization catalyst of the present disclosure has an amorphous silica alumina base impregnated with about 0.5 wt% to about 15 wt% nickel, in the form of 3.175 mm (0.125 inch) extrudates and a density of about 0.45 g / ml to about 0.65 g / ml. It is also contemplated that the metals can be incorporated onto the support by other methods such as ion exchange and co-milling.

[0082] The second stage oligomerization catalyst can be regenerated upon deactivation. Suitable regeneration conditions include subjecting the catalyst to hot air at about 400 °C to about 500 °C for 3 hours, for example, in situ. To facilitate regeneration without shutdown, a swing bed arrangement can be employed with an alternative second stage oligomerization reactor. The regeneration gas can include air with increased or decreased oxygen concentration. The activity and selectivity of the regenerated catalyst are comparable to fresh catalyst.

[0083] The second stage oligomerization reaction is also substantially exothermic. The last oligomerized olefin stream in line 224d includes a diluent stream from diluent line 214 that is added to the first olefin stream in line 212a and carried through the first stage oligomerization catalyst beds 222a to 222d. The diluent stream is then transported in line 228 to the second stage oligomerization reactor 232 to absorb the exotherm in the second stage oligomerization reactor. It is also contemplated that a dedicated diluent line to the second stage oligomerization reactor 232 for rapid control of the exotherm rise or to cool the second stage oligomerization reactor 232 and desirably only the second stage.

[0084] When the oligomerization reaction is performed according to the process conditions described above, a C4 olefin conversion of greater than or equal to about 95%, or greater than or equal to 97% is achieved. The resulting second stage oligomer stream in line 234 includes a plurality of olefin products that are hydrocarbons of distillate boiling range.

[0085] The oligomerized olefin stream in line 234, which has an increased concentration of C8+ olefins compared to the charged first stage oligomerization stream in line 228, is heat exchanged with the first stage oligomerization stream in line 224d, reduced in pressure, then heat exchanged with the olefin splitter column bottoms stream in line 230 and fed to dealkanizer column 240. The oligomerized olefin stream in line 234 is at a temperature of about 160°C (320°F) to about 190°C (374°F) and a pressure of about 3.9 MPa (gauge) (550 psig) to about 7 MPa (gauge) (1000 psig).

[0086] We have discovered that light alkanes, such as ethane and / or propane, are produced in the first stage oligomerization reactor 222 and / or the second stage oligomerization reactor 232, which must be removed from the second stage oligomerization stream for fuel production, particularly to facilitate light olefin recycle to the first stage oligomerization reactor 222. The light alkanes are inert and will accumulate in the recycle loop. Accordingly, the second stage oligomerization stream in line 234 is dealkanized by fractionation in dealkanizer column 240 to provide a light alkane stream and a dealkanized stream. In one embodiment, the light alkane stream is an ethane stream, in which case the dealkanizer column 240 is a deethanizer. In another embodiment, the light alkane stream is a propane stream, in which case the dealkanizer column 240 is a depropanizer. The alkane stream can also be a mixture of ethane and propane. The alkane stream can be used as fuel to provide heat duty in the process 210.

[0087] In the dealkanizer column 240, light alkanes, such as C3- hydrocarbons and suitably C2- hydrocarbons, can be separated from a dealkanized bottoms stream comprising C4+ hydrocarbons and suitably C3+ hydrocarbons, which can be in a bottoms line 244, in an alkane overhead stream, which can be in an overhead line 242. If operated as a deethanizer, the dealkanizer column 240 can be operated at a bottoms temperature of about 177°C (-350°F) to about 302°C (575°F) and a head pressure of about 207 kPa (gauge) (30 psig) to about -690 kPa (gauge) (100 psig). If operated as a depropanizer, the dealkanizer column 240 can be operated at a bottoms temperature of about 194°C (-381°F) to about 333°C (630°F) and a head pressure of about 207 kPa (gauge) (30 psig) to about 1.14 MPa (gauge) (165 psig).

[0088] The alkane overhead stream in overhead line 242 can be cooled and separated in dealkanizer receiver 246 to provide a dealkanized off-gas in off-gas line 247, which can be cooled and fed to further processing, such as being taken off as fuel gas in line 248 along with a net vapor stream in receiver overhead line 268. Condensate from dealkanizer receiver 246 can be refluxed back to dealkanizer 240 in dealkanizer overhead liquid line 249. In one embodiment, some of the condensate from dealkanizer receiver 246 in line 249 can be taken as a recycle in line 251 to the first stage oligomerization reactor in lines 272 and 226. The dealkanized stream that can be in bottoms line 244 can be split between a reboil stream in line 250 that is reboiled by heat exchange with a first hot diesel stream in line 252, which can be taken from the jet fuel fractionator bottoms heat exchange stream in jet fuel bottoms heat exchange line 274, and a net bottoms stream in line 254 that can be fed directly to the olefin splitter column 260 without heating. The reboiled bottoms stream in line 250 can boil back to dealkanizer 240 to provide the heating requirement. In another embodiment, the feed to dealkanizer 240 is not preheated by the olefin splitter column bottoms stream in line 230, but the feed to the olefin splitter column 260 in net bottoms line 254 will be preheated by the olefin splitter column bottoms stream.

[0089] The dealkanized stream in dealkanizer net bottoms line 254 is split into a light olefin stream, which can be in an olefin splitter overhead line 262, and a heavy olefin stream, which can be in an olefin splitter bottoms line 264, by fractionation in an olefin splitter column 260. The olefin splitter overhead stream can be cooled to about 66°C (150°F) to about 93°C (200°F), and the resulting condensate portion is refluxed from an olefin splitter receiver 266 back to the olefin splitter column 260. A net vapor stream in a receiver overhead line 268 from the olefin splitter receiver 266 can be cooled and further processed, such as a fuel gas in line 248 and an offgas stream in offgas line 247. The light olefin condensate from the bottom of the olefin splitter receiver in line 270 can be split between a reflux stream that is refluxed back to the column in line 271 and a light olefin recycle stream in recycle line 272, which can be recycled to the first stage oligomerization reactor 222 or alternatively to the second stage oligomerization reactor 232. The light olefin stream in line 272 can constitute about 1 wt% to about 15 wt% of the light olefin stream in line 270. The light olefin stream in line 272 can include about 40 wt% to about 80 wt% C4-C8olefins. In one embodiment, the light olefin stream in line 272 can be flashed in a knockout drum 275 to remove vapor in a light olefin vapor stream, which can be conveyed in an overhead line 277 to the hydrogenation section, and the liquid recycle olefin oligomer stream in line 226 can be recycled to the first stage oligomerization reactor 222 to oligomerize C4-C8olefins. Stream 280 is shown exiting after passing through a heat exchanger.

[0090] Steam is fed from steam generators (first steam generator 218a through first steam line 233a, second steam generator 218b through second steam line 233b, third steam generator 218c through third steam line 233c, fourth steam generator 218d through fourth steam line 233d, and fifth steam generator 218e through fifth steam line 233e) into a combined steam line 33, which is shown as being passed to provide steam to Figure 1 the ethanol dehydration reactor in line 188 (steam line 233). In one aspect, line 188 (steam line 233) is shown as being passed to provide steam to the ethanol dehydration reactor in line 188 (steam line 233). In one aspect, line 188 (steam line 233) is shown as being passed to provide steam to the ethanol dehydration reactor in line 188 (steam line 233). Figure 1A portion of the treated water stream in line 288 is taken and passed to the first steam generator 218a, the second steam generator 218b, the third steam generator 218c, the fourth steam generator 218d, and the fifth steam generator 218e. In one embodiment, the treated water stream in line 288 is split into five treated water streams: a first treated water stream in line 288a, a second treated water stream in line 288b, a third treated water stream in line 288c, a fourth treated water stream in line 288d, and a fifth treated water stream in line 288e. The first treated water stream in line 288a can be passed to the first steam generator 218a to produce a first steam stream in line 233a. The second treated water stream in line 288b can be passed to the second steam generator 218b to produce a second steam stream in line 233b. The third treated water stream in line 288c can be passed to the third steam generator 218c to produce a third steam stream in line 233c. The fourth treated water stream in line 288d can be passed to the fourth steam generator 218d to produce a fourth steam stream in line 233d. The fifth treated water stream in line 288e can be passed to the fifth steam generator 218e to produce a fifth steam stream in line 233e. The first steam stream in line 233a, the second steam stream in line 233b, the third steam stream in line 233c, the fourth steam stream in line 233d, and the fifth steam stream in line 233e are combined to provide a combined steam stream in line 33. The combined steam stream in line 33 is mixed with the first charge stream in line 30 and passed to the ethanol dehydration reactor in line 31. Figure 1 Additional steam generators can be present as needed, and in one configuration, there are seven steam generators that meet the process steam demand of the upstream ethanol dehydration unit. Process steam is generated using treated process water, and the use of boiler feed water is avoided. This is done to reduce the net wastewater amount. In one aspect, all of the treated water stream in line 188 Figure 1 The entire treated water stream in line 288 is taken and passed to the first steam generator 218a, the second steam generator 218b, the third steam generator 218c, the fourth steam generator 218d, and the fifth steam generator 218e to produce steam in line 33.

[0091] The total demand for process steam is very high compared to the steam production of the reactor section steam generators. Therefore, a dedicated hot diesel driven steam generator is provided to generate the balance process steam. This steam generator uses hot diesel as the heating medium, which is pumped from the jet fuel splitter reboiler pump back to the inlet of the jet fuel splitter reboiler heater.

[0092] The combined process steam is superheated by exchanging heat with the olefin splitter column bottoms in a steam superheater and then sent to the ethanol dehydration unit under pressure control.

[0093] When steam is generated with treated process water, there is a potential risk of steam kettle fouling. Once fouling is identified, the affected steam generator can be isolated for maintenance. A common backup steam generator is provided that can replace the fouled steam generator.

[0094] Specific embodiments

[0095] While the following is described in conjunction with specific embodiments, it will be understood that it is intended to cover all alternatives, modifications and equivalents as can be included within the scope of the preceding description and the appended claims.

[0096] A first embodiment of the present disclosure is a method for operating a dehydration reactor comprising adding an amount of steam to a feed to the dehydration reactor, wherein the steam is taken from an oligomerization section of a hydrocarbon conversion plant. An embodiment of the present disclosure is one, any or all of the previous embodiments in this paragraph through the first embodiment in this paragraph, wherein the steam is produced from treated process water produced by a waste water stripping column and then the water is sent to at least one steam generator connected to an oligomerization reactor to produce steam, and wherein a portion of the steam is sent to the dehydration reactor. An embodiment of the present disclosure is one, any or all of the previous embodiments in this paragraph through the first embodiment in this paragraph, wherein a portion of the feed water is blown down from each of the at least one steam generator. An embodiment of the present disclosure is one, any or all of the previous embodiments in this paragraph through the first embodiment in this paragraph, wherein a portion of the steam is sent from a hydrogenation reactor. An embodiment of the present disclosure is one, any or all of the previous embodiments in this paragraph through the first embodiment in this paragraph, wherein the steam cools a hot effluent by a minimum amount to at most about 187°C. An embodiment of the present disclosure is one, any or all of the previous embodiments in this paragraph through the first embodiment in this paragraph, wherein a ratio of steam to alcohol in the dehydration reactor is from about 0.3 weight / weight to about 5.0 weight / weight. An embodiment of the present disclosure is one, any or all of the previous embodiments in this paragraph through the first embodiment in this paragraph, wherein a portion of the steam is produced in a dedicated steam generator. An embodiment of the present disclosure is one, any or all of the previous embodiments in this paragraph through the first embodiment in this paragraph, wherein the steam is further heated by exchanging heat with an olefin splitter column bottoms stream in a steam superheater. An embodiment of the present disclosure is one, any or all of the previous embodiments in this paragraph through the first embodiment in this paragraph, wherein multiple steam generators are used to produce the steam. An embodiment of the present disclosure is one, any or all of the previous embodiments in this paragraph through the first embodiment in this paragraph, wherein a cycle oil steam generator cools hot cycle oil from a flash stripper column feed-cycle oil exchanger. An embodiment of the present disclosure is one, any or all of the previous embodiments in this paragraph through the first embodiment in this paragraph, wherein the oligomerization section comprises an oligomerization reactor comprising a first oligomerization reaction vessel and a second oligomerization reaction vessel. An embodiment of the present disclosure is one, any or all of the previous embodiments in this paragraph through the first embodiment in this paragraph, further comprising an intermediate cooler steam generator to remove heat of reaction from an oligomer effluent stream prior to passing the oligomer effluent stream to the second oligomerization reaction vessel.Embodiments of the present disclosure are one, any or all of the previous embodiments in this paragraph through the first embodiment in this paragraph, further comprising an intermediate cooler steam generator between oligomerization catalyst beds in the first oligomerization reactor vessel to remove heat of reaction from the oligomerization effluent stream of the top oligomerization catalyst bed of the first oligomerization reactor vessel. Embodiments of the present disclosure are one, any or all of the previous embodiments in this paragraph through the first embodiment in this paragraph, further comprising an intermediate cooler steam generator between oligomerization catalyst beds in the second oligomerization reactor vessel to remove heat of reaction from the oligomerization effluent stream of the top oligomerization catalyst bed of the second oligomerization reactor vessel. Embodiments of the present disclosure are one, any or all of the previous embodiments in this paragraph through the first embodiment in this paragraph, wherein the oligomerization section comprises a first stage oligomerization reactor and a second stage oligomerization reactor, and wherein an intermediate cooler steam generator is provided to remove heat of reaction from the oligomerization effluent stream of the first stage oligomerization reactor prior to passing the oligomerization effluent stream to the second stage oligomerization reactor.

[0097] A second embodiment of the present disclosure is a method for operating a dehydration reactor, comprising adding a steam stream to a feed to the dehydration reactor to produce a charged stream; dehydrating the charged stream to produce a dehydrated stream; cooling the dehydrated stream to separate a water stream; and producing the steam stream from the separated water stream. Embodiments of the present disclosure are one, any or all of the previous embodiments in this paragraph through the second embodiment in this paragraph, further comprising passing the separated water stream to an oligomerization section to produce the steam stream. Embodiments of the present disclosure are one, any or all of the previous embodiments in this paragraph through the second embodiment in this paragraph, further comprising passing the separated water stream to a wastewater stripping column to produce a stripped water stream; and passing the stripped water stream to the oligomerization section to produce the steam stream. Embodiments of the present disclosure are one, any or all of the previous embodiments in this paragraph through the second embodiment in this paragraph, further comprising heating the separated water stream with an olefin charged stream of the oligomerization section to produce the steam stream.

[0098] A third embodiment of the present disclosure is a method for operating a dehydration reactor, comprising adding a steam stream to a feed to the dehydration reactor to produce a charged stream; dehydrating the charged stream to produce a dehydrated stream; cooling the dehydrated stream to separate a water stream; and heating the separated water stream with an olefin charged stream of an oligomerization section to produce the steam stream.

[0099] While the foregoing description has been made in the context of particular embodiments, it is to be understood that the disclosure can be carried out in ways other than those specifically set forth without departing from the spirit and essential characteristics of the disclosure. Thus, the foregoing description is to be considered as illustrative only and not as restricting the remainder of the disclosure and is intended to encompass variations and modifications that can be apparent to those of ordinary skill in the art, coming within the scope of the appended claims. The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

[0100] In the foregoing, all temperatures are presented in degrees Celsius and all parts and percentages are by weight unless otherwise indicated.

Claims

1. A method for operating a dehydration reactor, the method comprising adding an amount of steam to a feed to the dehydration reactor, wherein the steam is taken from an oligomerization section of a hydrocarbon conversion plant.

2. The method of claim 1, wherein the steam is produced from treated process water produced by a waste water stripping column and then the water is sent to at least one steam generator connected to an oligomerization reactor to produce steam, and wherein a portion of the steam is sent to the dehydration reactor.

3. The method of claim 1, wherein a portion of the feed water is blown down from each steam generator of the at least one steam generator.

4. The method of claim 1, wherein a portion of the steam is sent from a hydrogenation reactor.

5. The method of claim 1, wherein a ratio of steam to alcohol in the dehydration reactor is from about 0.3 weight / weight to about 5.0 weight / weight.

6. The method of claim 1, wherein the steam is further heated by exchanging heat with an olefin splitter column bottoms stream in a steam superheater.

7. The method of claim 1, wherein a cycle oil steam generator cools hot cycle oil from a flash stripper column feed-cycle oil exchanger.

8. The method of claim 1, wherein the oligomerization section comprises an oligomerization reactor comprising a first oligomerization reaction vessel and a second oligomerization reaction vessel.

9. The method of claim 8, further comprising an intercooler steam generator to remove heat of reaction from an oligomer effluent stream before passing the oligomer effluent stream to the second oligomerization reaction vessel.

10. The method of claim 8, further comprising an intercooler steam generator between oligomerization catalyst beds in the first oligomerization reaction vessel to remove heat of reaction from an oligomer effluent stream of a top oligomerization catalyst bed of the first oligomerization reaction vessel, or further comprising an intercooler steam generator between oligomerization catalyst beds in the second oligomerization reaction vessel to remove heat of reaction from an oligomer effluent stream of a top oligomerization catalyst bed of the second oligomerization reaction vessel.

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